1. Field of the Invention
This invention relates to the extraction of crude oil from oil shale by hydrogenating low-temperature carbonization of oil shale.
2. Description of the Prior Art
In oil sands and oil shale, considerable reserves of crude oil are stored. The extraction of crude oil from these reserves is expensive. Efforts are being made, therefore, to develop less expensive processes for such extraction.
In a known method of extracting oil from oil shale, as disclosed in U.S. Pat. No. 3,617,472, the shale is subjected to hydrogenating low temperature carbonization in a reactor. In this process, carbon monoxide and hydrogen, which are produced by the partial oxidation of gaseous by-products of the separating process, act upon the shale, which has been mechanically prepared. In order to improve the yield of crude oil, water or steam can be additionally supplied to the reactor. In another known method, as disclosed in U.S. Pat. No. 3,617,469, the oil shale, in finely ground form, is first mixed with a heavy oil to form a slurry, the heavy oil emanating from the extraction process itself and being an aromatic solvent. Following the hydrogenating low temperature carbonization, which takes place under pressure, the gaseous low temperature carbonization mixture is first separated from the used oil shale and, subsequently, the gaseous low temperature carbonization mixture is separated into gaseous and liquid low temperature carbonization products and also water. Hydrogen in the gaseous products is recycled. In order to recover the heat which is contained in the used oil shale, it is further known to pass the oil shale through a cooling zone (U.S. Pat. No. 3,475,319) or to mix it with fresh oil shale (German Offenlegungsschrift No. 2,429,767).